Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $67.58   8.347%   $73.2209   $73.22   $73.20   $73.20  
  Purchase #2 $117.84   7.597%   $126.7923   $126.79   $126.80   $126.80  
  Purchase #3 $212.80   13.208%   $240.9066   $240.91   $240.90   $240.90  
  Purchase #4 $6.44   11.278%   $7.1663   $7.17   $7.15   $7.20  
  Purchase #5 $96.84   13.573%   $109.9841   $109.98   $110.00   $110.00  
  Purchase #6 $198.98   5.143%   $209.2135   $209.21   $209.20   $209.20  
  Purchase #7 $91.61   3.376%   $94.7028   $94.70   $94.70   $94.70  
  7 purchase totals = $792.09       $861.9865   $861.98   $861.95   $862.00